NSW INDEPENDENT TRIAL EXAMS – 2013
CHEMISTRY PRELIMINARY YR11 PRELIMINARY
MARKING GUIDELINES
Section I
1
C
2
A
3
C
4
D
5
B
6
C
7
B
8
D
9
B
10
A
11
D
12
C
13
B
14
B
15
A
16
C
17
A
18
C
19
D
20
B
Section II
Question 21(a)
Criteria
 Sketches a clear model for the metallic bonding
 Sketches a model of an atom of a metal
Answer may include:
Mark
2
1
Delocalised
Metal ions
valence
electrons
Question 21(b)
Criteria
Mark
2
 Describes the type of bonding
 Relates the bonding to a property of metals
1
 Identifies the type of bonding OR identifies a property
Answer may include: The type of bonding is metallic bonding. Metals have a small number of valence
electrons that can easily move though the crystal structure. These mobile electrons make metals good
electrical conductors.
Question 22(a)
Criteria
 Provides a correctly balanced chemical equation including states
Answer may include: Ca(s) + Cl2(g) → CaCl2(s)
Mark
1
Question 22(b)
Criteria
 Provides the correct Lewis electron dot structures for reactants and products
 Indicates the correct valence state for the ions
 Provides a correct Lewis electron dot structure for a reactant OR a product AND
indicates the correct valence state for the ions
 Provides ONE correct Lewis electron dot structure
Answer may include:
Mark
3
2
1
Cl
Ca
+
Cl Cl
2+
Ca
Cl
-
NSW Independent Trial Exams 2013 – Chemistry Yr 11 Preliminary Exam: Marking Guide– Page 1
Question 23(a)
Criteria
 States the valency and formula
Answer may include: Valency = 4, formula is SiO2
Mark
1
Question 23(b)
Criteria
Mark
2
 Identifies the bond type in silica and
 Explains the relationship between the melting point and bonding in silica
1
 Identifies the bond type in silica or
 Explains the relationship between the melting point and bonding in silica
Answer may include: Silicon dioxide is a covalent network substance. It has very strong covalent
bonding, throughout the three-dimensional lattice. It requires a large amount of energy to separate the
atoms, so that it has a very high melting point.
Question 24(a)
Criteria
Mark
1
 Explains filtering as the most appropriate method
Answer may include: Filtering makes use of the difference in water solubility of the two compounds.
Question 24(b)
Criteria
 Calculates the mass of barium sulfate
 Calculates the percentage of barium sulfate in the sample
 Calculates the mass of dry residue OR calculates the mass of barium sulfate
Answer may include:
Mass of barium sulfate residue = 6.35 – 0.95 = 5.40 g
5.40
100
% barium sulfate in sample
=
×
= 34.7 %
15.55
Mark
2
1
1
Question 25
Criteria
 Identifies magnesium oxide and calculates the mass of each element
 Converts each mass to moles
 Calculates the empirical formula
 Identifies magnesium oxide and calculates the mass of each element
 Converts each mass to moles
 Identifies magnesium oxide and calculates the mass of each element
Answer may include:
Magnesium oxide is the reaction product.
Mass Mg = 0.753 g, Mass O = 0.489 g, %Mg = 60.63, %O = 39.37
n Mg = 60.63/24.31 = 2.49, n O = 39.37/16 = 2.46
Ratio Mg:O = 1:1. Empirical formula = MgO
Mark
3
2
1
NSW Independent Trial Exams 2013 – Chemistry Yr 11 Preliminary Exam: Marking Guide– Page 2
Question 26(a)
Criteria
 Axes scales linear (1 mark)
 Axes labelled, including units (1 mark)
 Line graph plotted correctly (1 mark)
Answer may include:
Question 26(b)
Criteria
 Predicts the radius using the line graph
Answer may include: In the range110-115 pm, from line graph.
Mark
3
Mark
1
Question 26(c)
Criteria
Mark
2
 Relates decreasing radius to increasing nuclear charge acting on electrons in the
valence level
1
 Identifies trend and relates to a relevant atomic property
Answer may include: Atomic radius generally decreases across this series of elements from the 2nd
period. As nuclear charge increases the valence shell, and filled levels, are drawn closer to the nucleus,
reducing atomic size.
Question 27(a)
Criteria
 Alloy named and its constituents identified
Answer may include: Bronze, an alloy of tin and copper
Mark
1
Question 27(b)
Criteria
Mark
2
 Increase in available metals explained AND ONE example named
1
 Increase in available metals explained OR ONE example named
Answer may include: More metals available due to development of extraction methods such as
electrolysis to separate a compound and isolate the metal. Example: aluminium can be extracted from
bauxite by electrolysis of alumina.
NSW Independent Trial Exams 2013 – Chemistry Yr 11 Preliminary Exam: Marking Guide– Page 3
Question 28(a)
Criteria
Mark
2
 Metals and chemicals used for investigation identified AND procedure outlined
1
 Metals and chemicals used for investigation identified OR procedure outlined
Answer may include: Copper, magnesium, zinc and calcium were reacted with water and dilute HCl. A
small piece of copper was placed into test tubes and 1–2 mL of water was added. Step repeated for
remaining 3 metals. Procedure repeated for copper, magnesium and zinc using dilute HCl. Calcium only
tested in water.
Question 28(b)
Criteria
Mark
1
 Identifies a property and relates it to metallic activity
Answer may include: Ionisation energy. The higher the ionisation energy, the lower is the activity of a
metal.
Question 29(a)
Criteria
Mark
2
 Describes the structure AND shape of NH3
1
 Describes the structure OR shape of NH3
Answer may include: The ammonia molecule consist of three hydrogen atoms bonded to a nitrogen atom
by covalent bonds. The molecule has the shape of a triangular pyramid with nitrogen at the apex and the
hydrogen atoms forming the base.
Question 29(b)
Criteria
Mark
3
 Provides a correct electron dot diagram showing a hydrogen bond
 Describes a hydrogen bond as an intermolecular force in terms of strength, electron
pairs and atoms required
2
 Provides a partially correct electron dot diagram showing a hydrogen bond
 Describes some details about a hydrogen bond
1
 Provides a partially correct electron dot diagram showing a hydrogen bond
OR
 Describes some details about a hydrogen bond
Answer may include: Hydrogen bonding is a relatively strong attractive force between some
molecules. A hydrogen atom in one ammonia molecule is attracted and attached to the unshared pair
of electrons on the N atom of another molecule.
..
N
H H H
..
N
H H H
NSW Independent Trial Exams 2013 – Chemistry Yr 11 Preliminary Exam: Marking Guide– Page 4
Question 30(a)
Criteria
Mark
2
 Provides a comparison by fully describing the ion arrangement in both states
1
 Fully describes the ion arrangement in one of the states
OR
 Provides a comparison by partly describing the ion arrangement in both states
Answer may include: KNO3 is ionic. When solid it is composed of positively and negatively charged
ions arranged in a fixed position, close together in a regular lattice. In aqueous solution, the ions are
separated from each other, free to move around, with each surrounded by a number of water
molecules.
Question 30(b)
Criteria
 Calculates the correct temperature change
 Correctly calculates the energy absorbed but incorrectly calculates the temperature
change
OR
 Incorrectly calculates the energy absorbed but then correctly calculates a temperature
change
Answer may include: n = m/M = 10g/101.11g mol−1 = 0.0989 mol KNO3
ΔH = ΔHsol × n = 36 kJ mol−1 × 0.0989 mol = 3.56 kJ = 3560 J
ΔH = −mCΔT
(m= mass H2O + mass KNO3 = 110 g)
ΔT = −ΔH/mC = −3560 J/(0.110 kg × 4.18 x 103 J K-1 kg-1) = −7.7 oC
Final temperature = (20 - 7.7) oC, = 12.3 oC
Question 31(a)
Criteria
 Provides a correct ionic equation
Answer may include: Pb2+(aq) + 2I− (aq) → PbI2(s)
Mark
2
1
Mark
1
Question 31(b)
Criteria
Mark
3
 Explains the shape of both sections of the graph in terms of limiting and excess
reagents
 Explains the significance of point A
2
 Explains the shape of both sections of the graph in terms of limiting and excess
reagents
OR
 Identifies the limiting and excess reagents in both sections of the graph AND explains
the significance of point A
1
 Identifies the limiting reagent in either sections of the graph
OR
 Identifies the significance of point A
Answer may include: Up to point A, iodide ion is the limiting reactant, and the mass of precipitate is a
linear function of the volume of sodium iodide solution. At point A the lead and iodide ions are in
their stoichiometric ratio (1:2) and neither is in excess. Beyond point A lead ion is the limiting
reactant, so that the mass of precipitate is constant.
NSW Independent Trial Exams 2013 – Chemistry Yr 11 Preliminary Exam: Marking Guide– Page 5
Question 32(a)
Criteria
Mark
2
 TWO relevant aspects are listed and correct reasons are given for each
1
 ONE relevant aspect is listed and a correct reason is given
Answer may include:
 The boiling flask is too full (over half way) and this could cause an overflow or a dangerous buildup of pressure.
 The water inlet and outlet tubes are in the wrong positions (and should be swapped). This will
cause inefficient cooling.
 The flask is being directly heated. The heat needs to be spread with wire gauze to avoid the glass
cracking and/or inefficient heating.
Question 32(b)
Criteria
 The property is identified
Answer may include: Boiling point difference
Mark
1
Question 32(c)
Criteria
 A relevant industrial mixture is identified
Answer may include: One of: petroleum, wine, esters, seawater (purification), etc
Mark
1
Question 33(a)
Criteria
 Volatility is defined
Answer may include: Volatility is a measure of how easily a substance turns into a vapour.
Mark
1
Question 33(b)
Criteria
Mark
2
 The relation between temperature and molecular kinetic energy is cited, and used to
explain changing vapour pressure
1
 The relation between temperature and molecular kinetic energy is cited, or changing
vapour pressure related to molecular energy.
Answer may include: Increasing temperature increases the kinetic energy of the octane molecules and
more molecules vaporise. The increased number of vapour molecules, and their increased energy,
exert a higher vapour pressure.
NSW Independent Trial Exams 2013 – Chemistry Yr 11 Preliminary Exam: Marking Guide– Page 6
Question 34(a)
Criteria
Mark
2
 A blue flame is identified and a correct justification based on energy is stated
1
 A blue flame is identified or a correct justification based on energy is stated
Answer may include: The blue flame is the most efficient for heating water as it produces the greatest
heat of combustion.
Question 34(b)
Criteria
 A correct and balanced equation, with states, is written
Answer may include: CH4(g) + 1½O2(g) → CO(g) + 2H2O(g)
Mark
1
Question 35(a)
Criteria
Mark
2
 A suitable method including control and experimental variables
1
 A suitable method partially is outlined
Answer may include: 5 mm length magnesium metal strips were added to 50 mL volumes of
hydrochloric acid at different concentrations, at the same initial temperature. The time for the metal to
dissolve was measured.
Question 35(b)
Criteria
Mark
1
 A correct conclusion is outlined, relating reaction time to rate
Answer may include: As the concentration of the hydrochloric acid increased, the time for the reaction
decreased, indicating that the reaction rate had increased.
NSW Independent Trial Exams 2013 – Chemistry Yr 11 Preliminary Exam: Marking Guide– Page 7
NSW INDEPENDENT TRIAL EXAMS – 2013
CHEMISTRY PRELIMINARY HSC EXAMINATION
MAPPING GRID
Question
Marks
Content
Syllabus Outcomes
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21(a)
21(b)
22(a)
22(b)
23(a)
23(b)
24(a)
24(b)
25
26(a)
26(b)
26(c)
27(a)
27(b)
28(a)
28(b)
29(a)
29(b)
30(a)
30(b)
31(a)
31(b)
32(a)
32(b)
32(c)
33(a)
33(b)
34(a)
34(b)
35(a)
35(b)
TOTAL
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
1
3
1
2
1
2
3
3
1
2
1
2
2
1
2
3
2
2
1
3
2
1
1
1
2
2
1
2
1
75
8.2.3
8.2.1
8.2.3
8.2.5
8.2.4
8.3.5
8.3.4
8.3.2
8.3.3
8.3.2
8.3.4
8.3.4
8.4.3
8.4.4
8.4.2
8.4.5
8.5.1
8.5.2
8.5.3
8.5.5
8.2.5
8.2.5
8.2.3
8.2.3
8.2.1, 8.3.3
8.2.5
8.1, 8.2.1
8.2.1
8.3.4
8.1, 8.3.3
8.1
8.3.3
8.3.1
8.3.2
8.3.2
8.1, 8.3.2
8.4.2
8.4.2
8.4.3
8.4.5
8.4.4
8.4.4.
8.1, 8.5.3
8.5.3
8.5.3
8.5.3
8.5.3
8.5.4
8.5.4
8.5.5
8.5.5
2
3
6
14
7
4
10
8
6
11
10
4, 10
6, 8
10
6, 8
4, 7
1
9
2
8
6, 13
2, 13
1, 9
1, 6
1, 2
6, 14
1, 5
2, 14
6, 10
13
13
6
3
11
11
12
6
6, 13
6, 13
6, 7, 13
8, 13
8, 14
11
14
2
7, 8
7, 14
2
10
12
13, 14
Target Performance
Bands
3-4
2-3
3-4
4-5
3-4
3-4
3-5
3-5
3-5
3-4
4-6
4-5
4-5
3-4
3-4
2-3
2-3
2-3
3-4
4-5
2-3
4-5
3-4
4-5
2-3
3-4
2-3
3-4
3-5
3-4
1-2
3-5
2
3-5
2-5
3-5
3-4
3-5
2-4
3-4
3-4
2-6
3-4
2-3
3-4
3-4
2-3
2
3-4
4-5
3-4
NSW Independent Trial Exams 2013 – Chemistry Yr 11 Preliminary Exam: Marking Guide– Page 8